Blish lock
From Free net encyclopedia
Image:Johnbellblish.jpgThe Blish Lock is a breech locking mechanism designed by John Bell Blish based upon his observation that under extreme pressures, certain dissimilar metals will resist movement with a force greater than normal friction laws would predict. In modern engineering terminology, it is considered to be an extreme manifestation of what is now called static friction, or stiction. His locking mechanism was used first in the Thompson submachine gun.
The Blish Lock was the result of observations made by Blish of large naval guns. He noticed that guns firing relatively light charges tended to have their breech blocks unscrew and fly open, but the breech blocks of guns firing heavy charges remained closed. Using his mathematical and analytical training, he concluded that dissimilar metals have a tendency to adhere to each other when subjected to very high pressure. This principle of metallic adhesion of dissimilar metals became known as the Blish Principle. It did not take Blish very long to put this knowledge to use in a delayed-blowback breech lock. He developed a working model that used a simple wedge as the lock, and was eventually assigned Template:US patent on March 9, 1915.
While this system was used in the Thompson, it was eventually found to be redundant. Any real advantages to the system were far outweighed by the additional cost associated with the device.